1. The Field of the Invention
The present invention relates generally to high speed telecommunications systems. More particularly, embodiments of the present invention relate to the transient use of a clock in a telecommunications system to reduce cross-talk propagated into the received or transmitted signal, and to the parity-driven initiation of the clock upon the detection of a parity error.
2. Background and Relevant Art
Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals. Typically, data transmission in such networks is implemented by way of an optical transmitter, such as a laser, while data reception is generally implemented by way of an optical receiver, an example of which is a photodiode.
Various other components are also employed by the optical transceiver to aid in the control of the optical transmit and receive components, as well as the processing of various data and other signals. For example, such optical transceivers typically include a driver (e.g., referred to as a “laser driver” when used to drive a laser signal) configured to control the operation of the optical transmitter in response to various control inputs. The optical transceiver also generally includes an amplifier (e.g., often referred to as a “post-amplifier”) configured to amplify a data signal received by the optical receiver. A controller circuit (hereinafter referred to the “controller”) controls the operation of the laser driver and post amplifier.
While there are a variety of signals used in the transceiver, the primary function of the transceiver is to receive signals over a receive path, and transmit signals over a transmit path. The receive path begins at the optical receiver, which receives the optical signal for conversion into an electrical signal. The receive path continues through the post-amplifier and to the signal consumer. The signal consumer may be a host connected to the transceiver or perhaps another transceiver. The transmit path begins at a signal source (such as a host connected to the transceiver or perhaps another transceiver). The transmit path continues through the laser driver and to the optical transmitter. It is critical to the operation of the transceiver that the control signals used for proper operation of the transceiver do not significantly degrade the signals in the receive and transmit paths through cross-talk. Otherwise, the error rate may increase given a certain power level.
One potential source of cross-talk into the receive and transmit signals is the system clock used to time communications within the transceiver. However, the system clock is typically with the controller on a different integrated circuit than the components involved with the receive and transmit paths. Accordingly, the system clock is relatively distant from the receive and transmit paths, thereby reducing the impact of cross-talk. Thus, cross-talk from the system clock is not considered to be a critical problem in conventional optical transceivers and telecommunications systems.
Nevertheless, there can be situations in which cross-talk is more significant as when, for example, the controller and clock circuits are integrated within the same chip as the circuitry embodying the actual receive and transmit paths. In this case, the distance between the clock and the receive and transmit paths would be more proximate. Therefore, what would be advantageous are configurations in which cross-talk introduced by the clock into the receive and transmit paths is reduced.